This invention relates to a capacitive distance sensor adapted to measure clearance between an objective electrode and an object as a function of electrical capacitance changes between them, and more particularly to capacitive measuring device applicable to a configuration measuring apparatus of the a surface of an object.
Capacitive distance sensors which are based on the principle that the capacitance between two capacitor plates is inversely proportional to the distance between them have been well known. These capacitive distance sensors have many advantages, like high sensitivity, high credibility, good response and a long durable life of the sensors in comparison of other type clearance sensors, like optical sensors, electromagnetic sensors, fluidic sensors and the like. For measuring accurately a small clearance distance with this distance sensor, it is essential that the sensor has a small face of the electrode plate and be positioned in a limited narrow range of a clearance, because a capacitive distance sensor measures a average distance in the face area of the electrode plate of the sensor and has an effective measurable range of clearance distance proportional to the face area of the electrode plate. For example, in the case of measuring to an accuracy of the order of 1 nanometer, the sensor must be positioned in the effective range of 100 of a clearance.
A capacitive distance sensor having a small face area can measure a distance of a restricted range of a clearance. A positioning this sensor adjacent to an object in the restricted range of a clearance is required a highly skilled technician or a complicated positioning device. When a configuration of a surface of an object is determined from the results of measuring distance, it is more difficult and wastes much time to position the sensor at a large number of the measuring point on an object.
The present invention has been devised to overcome above described problem associated with the use of the capacitive distance sensor.
Accordingly, it is an object of the present invention to provide an electrical capacitive distance sensor comprising a fixed frame, an objective electrode adjacent to an object, a supporting device for moving the objective electrode to position said probe in the effective measuring range of a clearance, a moving distance detecting means for detecting a moving distance of the objective electrode, a clearance detecting means for detecting a clearance distance between the objective electrode and the object, a calculating means for calculating a distance between the object and the frame based on the signals from the moving distance detecting means and the clearance detecting means.
It is another object of the present invention to provide an electrical capacitive distance sensor comprising a frame, an objective electrode adjacent to the object, a rod for carrying the objective electrode, a linear motor for moving axially the rod, a clearance detecting means for detecting a clearance distance between the objective electrode and the object based on a capacitance between them, a control means for controlling the linear motor depending on a signal from said clearance detecting means to position said objective electrode in the predetermined range of a clearance between them, a moving distance detecting means for detecting a distance of the objective electrode, a calculating means for calculating a distance between the object and the frame based on the signals from the moving distance detecting means and the clearance detecting means.
It is a further object of the present invention to provide a determining configuration apparatus adapted to determine a configuration of a surface of an object which comprises a capacitive distance sensor including a objective electrode, a supporting device for moving the objective electrode to position said probe in the predetermined range of a clearance between said probe and the object, a moving distance detecting means for detecting a moving distance of the objective electrode, a clearance detecting means for detecting a clearance distance between the objective electrode and the object based on a capacitance between them, a calculating means for calculating a distance between the object and the frame based on the signals from the moving distance detecting means and the clearance detecting means; a positioning device for moving relatively the objective electrode along the surface of the object; and a configuration determining means for determining the configuration of the surface of the object based on the signals from the calculating means.
A capacitive distance sensor of the present invention comprises an a moving distance detecting means for detecting a moving distance of the objective electrode, and a clearance detecting means for detecting a clearance distance between the objective electrode, therefore, this distance sensor can measure a wide range distance even using a objective electrode of small face area. Furthermore, the objective electrode is feedback controlled based on a signal of itself, it is easy to position it in a effective measurable range of clearance.